1. Field of the Invention
The present invention relates the method for increasing isolation ability, more particularly by forming the shallow trench neighbouring between BN.sup.+ ROM cell.
2. Description of the Prior Art
Basically the new fashion way, to semiconductor device will be gradually fabricated smaller than before. Especially for the new generation, the manufactured technology for ROM of semiconductor device will be advantageously the coming twenty-first century. The ideal memory would be low cost, high performance, high density, with low power dissipation, random access, non-volatile, easy to test, highly reliable, and standardized throughout the industry. Also, the better cell isolation is expected for increasing the strength of device anti-punch through. Unfortunately those memory technologies which did not offer these advantages to some extent were one by one successfully challenged by the ROM memories. Therefore, how to improve the better cell isolation performance could not wait too long.